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Department of Chemical Engineering and Biotechnology

Iron nanoparticles

PhD student, Julien Mahin, from our Process Integration group, has developed a new method to produce single-sized magnetic nanoparticles with promising medicinal applications.

His research, under the supervision of Dr Laura Torrente, makes use of a continuous synthesis process capable of producing uniform magnetic iron nanoparticles. The particles have many potential applications, including as MRI contrast agents or cancer treatments.

Magnetic nanoparticles can be made from several different metals, but there is a lot of interest in those composed of iron or iron oxide, as these are non-toxic. Current molecules used as contrast agents in MRI scans to make the images clearer, are based on gadolinium, which has potential toxicity issues, particularly for patients with kidney disease. Iron nanoparticles offer a non-toxic alternative, but current production methods cannot effectively control the size distribution of particles.

“It’s challenging because what you're trying to do is control material formation on a very, very small scale – a few nanometres,” says Mahin. “What's important for biomedical applications is that you know exactly what you're putting in your body. When pharmaceutical companies develop drugs, they want to know exactly what's in it and it takes a long time to make sure it's safe. With nanoparticles, size is one of the most important properties because it will determine other properties of the particle so we need to have particles of a very well defined size.”

Current processes for making nanoparticles involve a batch process, where the different components are added together, heated, or put under required reaction conditions, and the nanoparticle product forms. But with this approach, batch to batch variations in particle size are unavoidable – the process is so sensitive to slight changes in conditions and it is incredibly difficult to ensure each batch is prepared in exactly the same way. The variation is often in particle size, which determines many of the physical and chemical properties of a nanoparticle.

Dr Torrente’s group are developing continuous synthesis methods to replace batch processes. Mahin has designed a custom reactor into which the starting components can be continuously pumped and the iron nanoparticle product, continuously obtained. While these methods have previously been applied to iron oxide nanoparticles, this is the first synthesis of metallic iron nanoparticles, which are of considerable interest due to their higher magnetisation.

“By using continuous processes, then because you're always injecting the reactants at the beginning, and they mix in a very controlled way, then you should always get the same product at the exit of the reactor,” explains Mahin. “So that solves the reproducibility issues, which is one of the big challenges of this field. We only get one size of nanoparticle that's very well defined in this method.”

As well as MRI contrast agents, iron nanoparticles could potentially be used to treat cancer in a process known as magnetic hyperthermia. When magnetic nanoparticles are exposed to an alternating magnetic field, their movement can generate heat. If the particles can be targeted to seek out tumours in the body, a magnetic field could be applied and the heat generated would kill the neighbouring cancer cells. This treatment has been the focus of research efforts for a number of years, but the production of the nanoparticles themselves remains a barrier. Metallic iron nanoparticles due to their higher magnetization provide more heating power compared to iron oxide.

Mahin is hoping that his continuous synthesis reactor could bring the treatment closer to realisation.

“Something I'm working on is including functionalisation and coating of the particles within the same continuous process,” says Mahin.”So you can produce, coat and functionalise the nanoparticles all in a single step using our flow reactor.”

You can read the full paper, published recently in Chemical Engineering Journal.

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